package org.example.jdbc;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * JDBC执行查询语句;
 * 查询所有用户的用户名、密码、年龄;
 */
public class Demo04JDBC {
    public static void main(String[] args) {
        //自动关闭特性;
        try (Connection connection = DBUtil.getConnection();){
            Statement statement = connection.createStatement();
            /*
                1.写操作[增删改]: executeUpdate() 返回值为int类型;
                2.读操作[查]: executeQuery() 返回值为 ResultSet 集合;
                  resultSet.next():
                  1.判断是否存在下一个元素,存在返回true,否则返回false;
                  2.游标cursor初始位置在第一个元素之前;
             */
            ResultSet resultSet = statement.executeQuery("SELECT username, password, age FROM user");
            while (resultSet.next()){
                String username = resultSet.getString("username");
                String password = resultSet.getString("password");
                int age = resultSet.getInt("age");
                System.out.println(username + " " + password + " " + age);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}
